Astronomers observe biggest storm ever seen

Emma Woollacott, 13th September 2011

Astronomers say they've observed extreme brightness changes on a nearby brown dwarf that could indicate a storm more dramatic than any ever before seen on a planet.

The University of Toronto-led team of astronomers used an infrared camera on the 2.5m telescope at Las Campanas Observatory in Chile to capture repeated images of a brown dwarf dubbed 2MASS J21392676+0220226, or 2MASS 2139 for short, over several hours. In that short time span, they recorded the largest variations in brightness ever seen on a cool brown dwarf.

"We found that our target's brightness changed by a whopping 30 per cent in just under eight hours," says PhD candidate Jacqueline Radigan.

"The best explanation is that brighter and darker patches of its atmosphere are coming into our view as the brown dwarf spins on its axis," said Radigan.

The changes in brightness could indicate a gigantic storm, similar to but bigger than the Great Red Spot on Jupiter. Alternatively, the astronomers say they may be observing the hotter, deeper layers of its atmosphere through big holes in the cloud deck.

According to theoretical models, clouds form in brown dwarf and giant planet atmospheres when tiny dust grains made of silicates and metals condense. The depth and profile of 2MASS 2139's brightness variations changed over weeks and months, suggesting that cloud patterns in its atmosphere are evolving with time.

"Measuring how quickly cloud features change in brown dwarf atmospheres may allow us to infer atmospheric wind speeds eventually, and teach us about how winds are generated in brown dwarf and planetary atmospheres," says Radigan.